If you have hives that last longer than six weeks or recur over months or even years, they’re considered chronic. If you can’t identify the cause, they’re labeled chronic idiopathic urticaria (hives). Medication for Chronic Hives It’s easier to prevent hives if you know what triggers them and can avoid those culprits. If you can’t identity your triggers, your doctor may recommend one or more of these medications to help relieve symptoms: Antihistamines. Your first line of defense against chronic hives is longer-acting antihistamines, such as loratadine, fexofenadine, and cetirizine, says Stanley Fineman, MD, of Atlanta Allergy & Asthma, adjunct associate professor in the department of pediatrics, allergy division, at the Emory University School of Medicine, and a past president of the American College of Allergy, Asthma & Immunology. Your body releases substances called histamines during an allergic reaction. Blood vessels get the signal to dilate, which causes swelling. Antihistamines, available over the counter and by prescription, block that message. “Antihistamine medications should start helping pretty quickly — within an hour or two,” Dr. Fineman says. But you may need to allow up to two weeks to see if they help overall. Antihistamines don’t have serious side effects, but they may cause drowsiness and can make your mouth dry. Most people get at least some relief with antihistamines. However, Dr. Lamb says that some individuals may need a combination of antihistamines to control their hives, such as a sedating antihistamine at bedtime and a non-drowsy formula during the day. If antihistamines don’t help, your doctor might have you add H2 blockers, commonly used to treat heartburn. Histamines not only cause allergic reactions that can lead to hives, but also stimulate cells in the lining of your stomach that produce hydrochloric acid. Available H2 drugs are nizatidine, famotidine, cimetidine, and ranitidine.  They’re only effective for hives when used in combination with first-line antihistamines. Corticosteroids. If you don’t respond to antihistamines, your doctor may recommend corticosteroids, such as prednisone, for chronic hives. These drugs can be taken orally or by injection. Corticosteroids reduce inflammation.  Like antihistamines, they should work rather quickly, Fineman says. While corticosteroids are used to treat severe outbreaks of hives, they aren’t a long-term solution because of their side effects. You should take the lowest possible effective dose for the shortest amount of time because prolonged use of corticosteroids can cause weight gain and high blood pressure. Long-term use can also increase your risk for heart attack, liver cancer, and infections. Antidepressants. Some tricyclic antidepressants, such as doxepin, have antihistamine effects at low doses. Antidepressants may cause you to be dizzy or drowsy, so you might benefit from taking doxepin at bedtime to help relieve the itch of hives and allow you to sleep. You should see improvement fairly quickly. Omalizumab. This biologic drug was first created as an asthma treatment, but in 2014 it was also approved for treating chronic hives in people who haven’t responded to antihistamines. An injectable medication, it must be given by a healthcare provider, usually once a month. Omalizumab appears to be safe and effective for chronic hives, according to a study published in March 2013 in the New England Journal of Medicine. You may not see results right away — it may take a few weeks, Fineman says. Serious side effects are rare, but omalizumab can increase your risk for some forms of cancer and infection. There’s also the risk of severe allergic reaction (anaphylaxis) which requires immediate medical treatment with adrenaline (epinephrine). Leukotriene modifiers. When you come in contact with allergens that can trigger hives, your body releases chemicals that cause inflammation known as leukotrienes. Leukotriene modifiers are medications designed to stop this reaction. They should start working rapidly, but can take up to two weeks. Possible side effects are flu-like symptoms, headache, stomachache, congestion, and nervousness. Leukotrienes are best used in combination with antihistamines. Immunosuppressants. Hives can be an immune response, so suppressing your immune system with a drug like cyclosporine can help prevent them. These powerful medications should work fairly rapidly, Fineman says. Possible side effects include headache, nausea, and increased risk for infection. Treating Chronic Hives Should Be Individualized Medications should make your hives go away and stay away. “If you get better, you know your treatment is working,” Fineman says. If you don’t get better, talk to your doctor about trying a different medication or combination of medications, Lamb says. Allergy testing is also important to try to determine the cause of your hives, she says. Chronic hives can be associated underlying health condition such as thyroid issues, hormonal problems, and cancer in rare cases. “Every person is different,” Fineman says. “Your treatment should be individualized to how you respond.”